1. Technical Field
The present invention relates to a delay circuit for a low power ring oscillator, and more particularly, to a technology for improving an operation frequency of a delay circuit while simultaneously minimizing current consumption thereof.
2. Description of the Related Art
Recently, due to the demands for low cost and low power wireless radio, the use of Zigbee technology according to the IEEE 802.15.4 standard has increased. Therefore, solutions using Zigbee have been developed in various fields such as a smart grid power system, a building control, an LED illumination field, and the like.
In addition, the development of a wireless radio technology using Zigbee at 868/915 MHz has actively progressed due to an advantage of transmitting/receiving distance or the like. However, in the case of 900 MHz band, an area of an inductor used in an amplifier, a mixer, an oscillator, or the like is increased as compared to the known 2.4 GHz band. The inductor, therefore, is almost the size of a chip, such that the manufacturing cost of a Zigbee chip is increased.
There is thus an increasing demand for an oscillator that does not use an inductor, as an oscillator for a wireless radio at 900 MHz band. As an example of the oscillator, the use of a ring oscillator has been recently considered. However, the ring oscillator has disadvantages such as high phase noise, a narrow frequency range, and large current consumption, as compared to the known LC oscillator. Therefore, there is a demand for a delay circuit capable of overcoming the disadvantages of such a ring oscillator.